WooCommerce Variations as Radio Buttons (PHP) -> functions.php (Result: https://i.imgur.com/dVlt07f.png) tutorial from https://stackoverflow.com/questions/36219833/woocommerce-variations-as-radio-buttons

WooCommerce Variations as Radio Buttons.css

/*Variations on single product*/
.single-product .variations .variation-radios input[type='radio']{
  display: none;
}
.single-product .variations .variation-radios label {
    border: 2px solid #ddd;
    border-radius: 4px;
    cursor: pointer;
    padding: 3px 6px;
    margin-right: 5px;
}
.single-product .variations select {
    display: none;
}
.single-product .variations .variation-radios label.selected-variation {
    border: 2px solid #13476F;
    color: #13476F;
}

WooCommerce Variations as Radio Buttons.js

    // Variable products variations label buttons from dropdown
    jQuery(document).on('change', '.variation-radios input', function() {
        jQuery('select[name="'+jQuery(this).attr('name')+'"]').val(jQuery(this).val()).trigger('change');

        jQuery('.variation-radios label').each(function(index, element) {
            jQuery(this).removeClass('selected-variation');
        });

        var attribute_value = jQuery(this).val();
        jQuery('.variation-radios label[for="'+attribute_value+'"]').addClass('selected-variation');
    });
    jQuery(document).on('woocommerce_update_variation_values', function() {
        jQuery('.variation-radios input').each(function(index, element) {
            jQuery(element).removeAttr('disabled');
            var thisName = jQuery(element).attr('name');
            var thisVal  = jQuery(element).attr('value');
            if(jQuery('select[name="'+thisName+'"] option[value="'+thisVal+'"]').is(':disabled')) {
                jQuery(element).prop('disabled', true);
            }
        });
    });

WooCommerce Variations as Radio Buttons.php

<?php 
function variation_radio_buttons($html, $args) {
  $args = wp_parse_args(apply_filters('woocommerce_dropdown_variation_attribute_options_args', $args), array(
    'options'          => false,
    'attribute'        => false,
    'product'          => false,
    'selected'         => false,
    'name'             => '',
    'id'               => '',
    'class'            => '',
    'show_option_none' => __('Choose an option', 'woocommerce'),
  ));

  if(false === $args['selected'] && $args['attribute'] && $args['product'] instanceof WC_Product) {
    $selected_key     = 'attribute_'.sanitize_title($args['attribute']);
    $args['selected'] = isset($_REQUEST[$selected_key]) ? wc_clean(wp_unslash($_REQUEST[$selected_key])) : $args['product']->get_variation_default_attribute($args['attribute']);
  }

  $options               = $args['options'];
  $product               = $args['product'];
  $attribute             = $args['attribute'];
  $name                  = $args['name'] ? $args['name'] : 'attribute_'.sanitize_title($attribute);
  $id                    = $args['id'] ? $args['id'] : sanitize_title($attribute);
  $class                 = $args['class'];
  $show_option_none      = (bool)$args['show_option_none'];
  $show_option_none_text = $args['show_option_none'] ? $args['show_option_none'] : __('Choose an option', 'woocommerce');

  if(empty($options) && !empty($product) && !empty($attribute)) {
    $attributes = $product->get_variation_attributes();
    $options    = $attributes[$attribute];
  }

  $radios = '<div class="variation-radios">';

  if(!empty($options)) {
    if($product && taxonomy_exists($attribute)) {
      $terms = wc_get_product_terms($product->get_id(), $attribute, array(
        'fields' => 'all',
      ));

      foreach($terms as $term) {
        if(in_array($term->slug, $options, true)) {
          $radios .= '<input type="radio" name="'.esc_attr($name).'" id="'.esc_attr($term->slug).'" value="'.esc_attr($term->slug).'" '.checked(sanitize_title($args['selected']), $term->slug, false).'><label for="'.esc_attr($term->slug).'">'.esc_html(apply_filters('woocommerce_variation_option_name', $term->name)).'</label>';
        }
      }
    } else {
      foreach($options as $option) {
        $checked    = sanitize_title($args['selected']) === $args['selected'] ? checked($args['selected'], sanitize_title($option), false) : checked($args['selected'], $option, false);
        $radios    .= '<input type="radio" name="'.esc_attr($name).'" value="'.esc_attr($option).'" id="'.sanitize_title($option).'" '.$checked.'><label for="'.sanitize_title($option).'">'.esc_html(apply_filters('woocommerce_variation_option_name', $option)).'</label>';
      }
    }
  }

  $radios .= '</div>';

  return $html.$radios;
}
add_filter('woocommerce_dropdown_variation_attribute_options_html', 'variation_radio_buttons', 20, 2);

function variation_check($active, $variation) {
  if(!$variation->is_in_stock() && !$variation->backorders_allowed()) {
    return false;
  }
  return $active;
}
add_filter('woocommerce_variation_is_active', 'variation_check', 10, 2);